Scrotum anatomy: the layers, septum and contents of the scrotal sac

What it is

The scrotum is the skin-covered sac that holds the testes, behind the penis and in front of the anus.

Location

It hangs below the root of the penis, between the thighs. Each of its two compartments holds a testis, an epididymis and the lower end of a spermatic cord.

Function

It keeps the testes outside the abdominal cavity, a few degrees cooler than the body core, which sperm production needs; the dartos and cremaster muscles raise or lower the testes to adjust their temperature.

Body system

Reproductive · single, midline structure · male body

FMA ID

FMA18252 (Foundational Model of Anatomy)

Key facts

• TeachMeAnatomy describes it as 'a fibromuscular cutaneous sac, located between the penis and anus', with the dartos muscle, a sheet of smooth muscle, immediately under the skin.
• A midline septum divides it into two compartments, one for each testis.
• In the 3D model the scrotum is an approximation built as a thin wall just inside the BodyParts3D skin around the testes; BodyParts3D has no separate scrotum.

The scrotum is a fibromuscular sac covered with skin, lying between the penis and the anus. It is dual-chambered and forms an expansion of the perineum. (TeachMeAnatomy: The Scrotum.)

Radiopaedia describes it as a dual-chambered protuberance of skin and muscle that contains the testes, the epididymides and the spermatic cords. The two chambers are separated by a septum. (Radiopaedia: Scrotum.)

OpenStax describes the scrotum as a skin-covered, highly pigmented, muscular sac. Keeping the testes there, outside the abdominal cavity, matters for sperm production, which is most efficient when the testes are 2 to 4 °C below core body temperature. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

The 3D model highlights the scrotum as an approximate part built for this site. BodyParts3D, the adult male data set behind the model, has no scrotum, so a thin wall about 2 mm thick was built just inside the body's skin around both testes and epididymides, open at its neck where the spermatic cords leave, with a built septum of the scrotum dividing it in two. It is drawn translucent so the testes and epididymides inside show through, and it exists only in the male body. Its upper edge follows the skin where it meets the thighs, so the sac flares slightly at the top in the front view. Real testis sizes and the temperature difference are given in the sections below.

Testes, ducts, seminal glands, prostate and penis, with the path of sperm. Male reproductive system.

From superficial to deep, the layers of the scrotal wall are the skin, the dartos fascia with its smooth muscle, the external spermatic fascia, the cremaster muscle, the internal spermatic fascia and the tunica vaginalis. These layers are continuations of the layers of the abdominal wall. (Patel AP. Anatomy and physiology of chronic scrotal pain. Transl Androl Urol. 2017.)

Radiopaedia lists the same order: pigmented skin with rugal folds; superficial fascia and dartos muscle; external spermatic fascia, a continuation of the external oblique aponeurosis; cremasteric fascia, a continuation of the internal oblique aponeurosis; internal spermatic fascia, a continuation of the transversalis fascia; the tunica vaginalis; and the tunica albuginea covering the testis. (Radiopaedia: Scrotum.)

Strictly, Kenhub counts only two layers as the scrotum itself, the skin and the dartos fascia, because the scrotum develops separately from the testes. The deeper layers are coverings of the testis brought down from the abdominal wall as the testis descended. (Kenhub: The scrotum.)

The scrotal skin is thin and corrugated (wrinkled) and rich in sebaceous glands. Under it lies a unique subcutaneous layer filled with smooth muscle fibres and with no fat. (Lin et al. Anatomical considerations, testicular, and scrotal anatomy of nonobstructive azoospermia patients. Asian J Androl. 2025.)

The dartos is a sheet of smooth muscle immediately under the skin. When it contracts it wrinkles the skin, which reduces the surface area and so reduces heat loss. (TeachMeAnatomy: The Scrotum.)

The dartos fascia is continuous with Scarpa fascia, the membranous layer of superficial fascia on the abdominal wall, and with the superficial fascia of the perineum (Colles fascia). (Radiopaedia: Scarpa fascia.)

The three spermatic fasciae wrap each testis and spermatic cord. From outermost to innermost: the external spermatic fascia comes from the aponeurosis of external oblique; the cremaster muscle and its fascia come from internal oblique; and the internal spermatic fascia comes from the transversalis fascia. (TeachMeAnatomy: The Spermatic Cord.)

Radiopaedia gives the same three coverings and explains them by descent: the testes drag the layers of the anterior abdominal wall with them as they move down into the scrotum. (Radiopaedia: Spermatic cord.)

The innermost layer, the tunica vaginalis, lies inside the internal spermatic fascia. It has a parietal and a visceral layer, normally separated by only a little fluid. (Lam Shin Cheung et al. A sound approach to stay on the ball: a review of scrotal pathologies on ultrasound imaging. Br J Radiol. 2026.)

The tunica vaginalis is what remains of the processus vaginalis, a pouch of peritoneum that pushed down through the abdominal wall during development. Its upper part closes off, and the lower part that envelops the testis becomes the tunica vaginalis. (Radiopaedia: Testicular development and descent.)

External oblique, internal oblique, transversus abdominis and the inguinal canal. Abdominal muscles.

The dartos muscle forms the subcutaneous muscle layer of the scrotum and continues inwards as the scrotal septum, a wall that divides the scrotum into two compartments, each holding one testis. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

Kenhub likewise describes the dartos fascia dividing the scrotum internally into right and left compartments through an internal fascial septum, one compartment for each testis. (Kenhub: The scrotum.)

Lin and colleagues add that the fat-free subcutaneous layer, together with the fascia of the spermatic cord, extends backwards to form the septum. (Lin et al. Anatomical considerations, testicular, and scrotal anatomy of nonobstructive azoospermia patients. Asian J Androl. 2025.)

On the outside, a ridge of skin called the scrotal raphe runs down the midline. It marks the line where the paired labioscrotal swellings fused in the embryo. (Kenhub: The scrotum.)

The midline partition between the two compartments, in the 3D model. Septum of scrotum.

The scrotum contains the testes, the epididymides, the testicular and epididymal appendages and the lower part of each spermatic cord. (Radiopaedia: Scrotum.)

Each testis is the site of sperm production; the epididymis stores sperm; and the spermatic cord is a collection of muscle fibres, vessels, nerves and ducts running to and from the testis. (TeachMeAnatomy: The Scrotum.)

Normal adult testes are ovoid, about 3 to 5 cm long and 2 to 3 cm across, with a volume of 15 to 25 mL. (Radiopaedia: Testis.)

A 2025 review gives the same sizes for healthy adult men: 3 to 5 cm long, 2 to 3 cm wide and 2 to 3 cm thick, with a volume of 15 to 25 mL. (Lin et al. Anatomical considerations, testicular, and scrotal anatomy of nonobstructive azoospermia patients. Asian J Androl. 2025.)

Apart from being attached to the bottom of the scrotum by the gubernaculum, which helps prevent twisting, each testis can move within its compartment. In most men the right testis rests a little higher than the left. (Patel AP. Anatomy and physiology of chronic scrotal pain. Transl Androl Urol. 2017.)

Lam Shin Cheung and colleagues also note that one testis, typically the left, may normally hang slightly lower than the other. (Lam Shin Cheung et al. A sound approach to stay on the ball: a review of scrotal pathologies on ultrasound imaging. Br J Radiol. 2026.)

The spermatic cord contains the ductus deferens, the testicular artery from the aorta, the cremasteric artery, the artery to the ductus deferens, the pampiniform plexus of veins, the genital branch of the genitofemoral nerve, autonomic nerves, lymphatic vessels and the closed remnant of the processus vaginalis. (TeachMeAnatomy: The Spermatic Cord.)

The testis in the 3D model: structure, blood supply and function. Testis.

The scrotal wall is supplied by three sets of arteries: the posterior scrotal branches of the perineal artery, the anterior scrotal branches of the external pudendal artery, and the cremasteric artery, a branch of the inferior epigastric artery. (Kenhub: The scrotum.)

TeachMeAnatomy gives the anterior scrotal artery as a branch of the external pudendal artery and the posterior scrotal artery as a branch of the internal pudendal artery. The scrotal veins follow the major arteries; TeachMeAnatomy names the external pudendal veins as their drainage. (TeachMeAnatomy: The Scrotum.)

The testis itself has a different supply. Each testis is fed by its testicular artery, which arises from the aorta just below the renal arteries. The pampiniform plexus drains the testis and ascends as the testicular vein: the right testicular vein drains directly into the inferior vena cava and the left into the left renal vein. (Radiopaedia: Testis.)

Patel describes the supply of the scrotum and its contents as rich and interconnected, with anastomoses between branches of the internal and external iliac arteries. The superficial veins of the scrotum mostly follow the arteries: the front drains through the external pudendal branches and the back through the internal pudendal branches to the internal iliac vein. He also describes the small veins of the pampiniform plexus joining to form the gonadal (testicular) vein, which empties into the left renal vein on the left and the inferior vena cava on the right. (Patel AP. Anatomy and physiology of chronic scrotal pain. Transl Androl Urol. 2017.)

Lymph from the scrotum drains to the nearby superficial inguinal lymph nodes in the groin. (TeachMeAnatomy: The Scrotum.)

Radiopaedia gives the same route for scrotal lymph, to the superficial inguinal nodes. (Radiopaedia: Scrotum.)

Lymph from the testis takes a completely different path. Its lymphatic vessels run up with the testicular arteries to the para-aortic lymph nodes on the back wall of the abdomen. (Radiopaedia: Testis.)

TeachMeAnatomy gives the same destination for the lymph vessels of the spermatic cord: the para-aortic nodes in the lumbar region. (TeachMeAnatomy: The Spermatic Cord.)

Patel explains the difference: lymph from the skin, the scrotal layers and the tunica vaginalis drains to the superficial and then deep inguinal nodes, while lymph from the testis and epididymis drains into the retroperitoneum along the route the testis took when it migrated down during development. (Patel AP. Anatomy and physiology of chronic scrotal pain. Transl Androl Urol. 2017.)

The inguinal region, inguinal canal and superficial inguinal lymph nodes. Groin.

The front and side of the scrotum are supplied by the genital branch of the genitofemoral nerve (L1, L2) and the anterior scrotal nerves, branches of the ilioinguinal nerve (L1). The back is supplied by the posterior scrotal nerves from the perineal branch of the pudendal nerve (S2 to S4), and the lower part by perineal branches of the posterior cutaneous nerve of the thigh. (Kenhub: The scrotum.)

Patel gives the same map: the genital branch of the genitofemoral nerve supplies the anterolateral surface, the anterior scrotal nerves from the ilioinguinal nerve the anterior surface, the posterior scrotal nerves from the pudendal nerve the posterior surface, and the long scrotal branches of the posterior femoral cutaneous nerve the inferior surface. Overall the somatic supply of the scrotum and testes comes from the L1 to L2 and S2 to S4 roots. (Patel AP. Anatomy and physiology of chronic scrotal pain. Transl Androl Urol. 2017.)

The genital branch of the genitofemoral nerve also supplies the cremaster muscle. Stroking the skin of the upper inner thigh makes the cremaster on the same side contract and lift the testis: in this cremasteric reflex the ilioinguinal nerve is the sensory limb and the genital branch of the genitofemoral nerve the motor limb. (Radiopaedia: Cremaster muscle.)

TeachMeAnatomy describes the same reflex, with the ilioinguinal nerve carrying the sensory signal into the spinal cord at L1 and the genital branch of the genitofemoral nerve carrying the motor signal. (TeachMeAnatomy: The Spermatic Cord.)

The scrotum develops from a pair of ridges, the labioscrotal swellings, which later fuse in the midline to form one continuous sac. The scrotal raphe marks the line of fusion. (Kenhub: The scrotum.)

TeachMeAnatomy also describes the scrotum forming from paired genital swellings that fuse in the midline, and notes that it is the biological homologue of the labia majora in females. (TeachMeAnatomy: The Scrotum.)

The testes develop from the gonadal ridge on the back wall of the abdomen. Each is attached to the gubernaculum, a band of mesenchyme that grows down towards the scrotal swellings, and a pouch of peritoneum, the processus vaginalis, pushes through the abdominal wall; together they form the inguinal canal. The testis lies within the deep inguinal ring by the 7th month and then descends into the scrotum over days to weeks. (Radiopaedia: Testicular development and descent.)

OpenStax places the descent through the abdominal musculature into the scrotum in the seventh month of fetal development. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

Ivanova and colleagues describe the gubernaculum as the mesenchymal tissue extending from the fetal testis and epididymis to the developing scrotum, and note that in humans testicular descent is complete at birth, at about the 35th week of gestation. (Ivanova et al. Gubernaculum and Epididymo-Testicular Descent: Review of the Literature. Acta Med Litu. 2022.)

Kenhub gives about 32 weeks for both testes to complete their descent from the back wall of the abdomen through the inguinal canal, so sources differ by a few weeks on the exact timing. If the testes do not descend into the scrotum but remain inside the body, the condition is called cryptorchidism. (Kenhub: The scrotum.)

Sperm production works best when the testes are kept 2 to 4 °C below core body temperature. The dartos and cremaster muscles contract together to raise the testes towards the body in cold weather, and relax to let them hang lower when it is warm. (OpenStax Anatomy and Physiology 2e, 27.1: Anatomy and Physiology of the Testicular Reproductive System.)

A review of scrotal imaging puts the scrotal temperature about 2 °C lower than the rest of the body. (Studniarek M et al. Scrotal imaging. J Ultrason. 2015.)

Inside the spermatic cord, the pampiniform plexus of veins acts as a heat exchanger, cooling the arterial blood before it reaches the testis. (TeachMeAnatomy: The Spermatic Cord.)

Radiopaedia describes the same heat-exchange role of the pampiniform veins, and explains that a varicocele disrupts it so that the testis warms towards core body temperature. (Radiopaedia: Varicocele.)

A hydrocele is a collection of serous fluid between the layers of the tunica vaginalis around a testis or spermatic cord. A congenital (communicating) hydrocele collects around a processus vaginalis that failed to close; acquired hydroceles can follow trauma, epididymitis, torsion, a tumour or infarction of the testis. (Radiopaedia: Hydrocele.)

Lam Shin Cheung and colleagues define a hydrocele as excess fluid within the tunica vaginalis; most cases have no known cause and show as painless scrotal swelling. (Lam Shin Cheung et al. A sound approach to stay on the ball: a review of scrotal pathologies on ultrasound imaging. Br J Radiol. 2026.)

A varicocele is a dilatation of the pampiniform plexus of veins. Radiopaedia estimates it in about 15% of the general male population and about 40% of subfertile and infertile men. Clinically significant varicoceles are about 85% left-sided, partly because the left testicular vein is longer and joins the left renal vein at a right angle. (Radiopaedia: Varicocele.)

A 2026 ultrasound review gives the same figures, varicocele in about 15% of males and up to 40% of infertile men, and explains that the vertical course of the left testicular vein predisposes to left-sided varicoceles. (Lam Shin Cheung et al. A sound approach to stay on the ball: a review of scrotal pathologies on ultrasound imaging. Br J Radiol. 2026.)

A 2015 review of scrotal imaging likewise places 85% of varicoceles on the left spermatic cord; isolated right-sided varicocele is rare. (Studniarek M et al. Scrotal imaging. J Ultrason. 2015.)

Testicular torsion is twisting of the testis on its spermatic cord, which cuts off its blood supply. The common intravaginal type, seen in adolescents and young adults, is linked to the bell clapper deformity, an abnormally high attachment of the tunica vaginalis to the cord. The cremasteric reflex is typically absent. (Radiopaedia: Testicular torsion.)

Lam Shin Cheung and colleagues describe torsion as a surgical emergency; the bell clapper deformity lets the cord move freely, and neonates and males around puberty are at highest risk. (Lam Shin Cheung et al. A sound approach to stay on the ball: a review of scrotal pathologies on ultrasound imaging. Br J Radiol. 2026.)

An indirect inguinal hernia, the most common type of abdominal hernia, enters the inguinal canal through the deep inguinal ring and in males may extend through the superficial ring into the scrotum. Radiopaedia links its male predominance to persistence of the processus vaginalis during testicular descent. (Radiopaedia: Indirect inguinal hernia.)

Radiopaedia's article on testicular descent adds that failure of the processus vaginalis to close, more common on the right, predisposes to an indirect inguinal hernia that occupies it, and that persistence of part of the processus can produce a hydrocele of the cord or testis. (Radiopaedia: Testicular development and descent.)

The nearest named structures in the 3D model, measured from the centre of each part:

• Skin · skin
• Testis · reproductive
• Septum of scrotum · reproductive
• Epididymis · reproductive
• Deferent duct · reproductive
• Femoral vein · cardiovascular
• Adductor longus · muscular
• Testicular artery · cardiovascular
• Great saphenous vein · cardiovascular
• Testicular vein · cardiovascular